Hypoxemia

Question 1

Define hypoxemia.

Answer 1

Hypoxemia is defined as SaO2 < 90% or PaO2 < 60 mmHg.

Question 2

What are the clinical features of hypoxemia?

Answer 2

Decreased SpO2
Cyanosis
Tachycardia
Dysrhythmias
Bradycardia-->asystole
Hypotension--> cardiovascular collapse

Question 3

What are the possible etiologies of hypoxemia?

Answer 3

1. Decreased FiO2
2. Hypoventilation
3. V/Q mismatch
4. Anatomic shunt
5. Excessive metabolic demand or decreased MvO2
6. Diffusion problem
   7: Abnormal hemoglobin species

Question 4

What is the management of hypoxemia?

Answer 4

1. FiO2 to 100% (verify)
2. Check adequacy of ventilation
   - check EtCO2
   - hand ventilate to check compliance
   - give recruitment breath
   - watch for chest rise and symmetry
   - consider PEEP
   - ABG, co-oximetry for abnormal Hgb
3. Check ETT position
4. Verify function of pulse oximeter
5. Suction ETT
6. Restore adequate circulating volume/add blood
7. Check for surgical cause of hypoxemia (e.g., retraction impeding ventilation)

Question 5

How might hypotension cause hypoxemia?

Answer 5

Ventilation goes to West Zone 1 preferentially and perfusion goes to West Zone 3 preferentially. Hypotension may augment the degree of this imbalance to a degree that results in hypoxemia.